[PATCH xserver] glamor: Cannot use copies when accessing outside of composite source

[Michel Dänzer]

On 28.05.2016 14:52, Keith Packard wrote:
> Michel Dänzer <michel at daenzer.net> writes:
> 
>> You know the details better than I do, but my understanding is that the
>> region can only be clipped to the destination in general, because
>> accessing source pictures outside of their boundaries is defined such
>> that it can change the contents of the destination.
> 
> Yeah, I didn't remember that the composite operation is supposed to do
> source clipping as there may be a transform involved. However, we need
> to make sure the rendered region is inside the source composite clip so
> that the simple copy will work correctly.
> 
>> Anyway, the fact is that this patch fixes a fair number of rendercheck
>> tests.
> 
> Here's a patch which uses region operations to make sure we don't use
> copy when the source doesn't contain all of the necessary bits. Note
> that this just means we'll fall back to the existing (broken) code which
> doesn't bother to clip against the source either, but at least that's
> only one bug instead of two?

Let's take things one step at a time, get my patch in as is (which
brings us back to where we were before using copies wrt correctness) and
then yours on top?


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer

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